Mercury ions exist in the environment as complex with inorganic and organic ligands or stabilized with sulfide ions forming cinnabar. Although inorganic mercury is less toxic than methylmercury or dimethylmercury, it is imperative that its concentration in sediment and waters be kept low since neutral dissolved inorganic mercury, such as neutral chloride species, can be transformed by sulfate reducing bacteria into toxic and bioaccumulative methylmercury or dimethylmercury. Much effort has been expended on developing techniques for mercury removal from water such as precipitation with elemental sulfur, ion exchange, membrane separation, and adsorption with zeolites, nanoparticles, and activated carbons.
Utilizing an adsorbent such as zeolite or activated carbon has drawn attention for economical reasons. Since sulfur has a high affinity for mercury, reduced sulfur functional groups, such as sulfide, thiol, and elemental sulfur, have been incorporated into adsorbents to enhance mercury sorption efficiency.
Sulfur-impregnated activated carbon enhances mercury removal efficiency from flue gas and from the aqueous phase. A general method for activated carbon sulfur impregnation is to treat the activated carbon with a mercury adsorbent such as elemental sulfur, polysulfide (Sx2−), thiol, or polythiol at high temperature (200-600° C.). Hg(0) removal efficiency on sulfur-impregnated activated carbon is dependent on sulfur impregnation method and temperature as well as the resulting micropore area of the sulfur-impregnated activated carbon. However, found that more than 20% of the elemental sulfur loading on activated carbon at reaction temperatures above 400° C. resulted in the loss of mercury removal efficiency due to the generation of less reactive sulfur species, blocking pores and reducing reactive surface area by the excessive sulfur loading. What is needed is are porous, low-cost and effective environmental toxin remediation particles that can be readily fabricated.